Method of returning oil from an element of a refrigeration system to the compressor thereof



Aug. 28, 1956 R. H. SWART 2,760,355

METHOD OF RETURING OIL FROM AN ELEMENT OF A REFRIGERATION SYSTEM TO THE COMPRESSOR THEREOF Original Filed Dec. 15, 1948 FIG.|

IN V EN TOR.

United States Patent Richard H. Swart, Syracuse, N. Y., assignor to Carrier Corporation, Syracuse, N. Y a corporation of Delaware.

Original application. December 15, 1948, Serial No.

65,487.. Divided and this application May 22', 1952,.

Serial No. 289,233

2 Claims. (Cl. 62-170) This application is a division of my pending application, Serial 65,487, filed December 1948, entitled Oil Return Mechanism for Refrigeration Systems now Patent No. 2,614,402, October 21, 1952, and relates to a methodv of returning. oil collected: in a refrigeration system to. the. compressor of thesystem while: restricting or blocking. free flow of liquid refrigerant from the evaporator to the compressor.

In the operation: of the usual. type refrigeration system, the compressor lubricant tends to mix with the refrigerant through oil. pumping by the compressor pistons. or by direct transfer of oil foam from the compressor. crankcase through the intake ports of the compressor and from thence into the refrigerant circuit. Such lubricant in solution with the refrigerant liquid reduces the efliciency of the heat transfer surfaces and also decreases the quantity of oil lubricant. in; the compressor crank case. It is necessary that some means be provided to return this lubricant to the compressor crankcase. In refrigeration systems having continuous evaporator tubing without any traps or accumulators, the lubricant is returned to the compressor with the refrigerant vapor which moves at high velocities. In a large majority of refrigerant systems, it is necessary to include a trap or accumulator as part of the system. In this type of system, the lubricant being non-volatile, tends to remain in the trap especially in systems where under some conditions of operation the trap is not supplied with liquid refrigerant. If no means are provided to return the contents of the trap to the crankcase of the compressor, lubrication failure of the compressor may ensue. Heretofore, means proposed to return this lubricant to the compressor were liable to return unevaporated liquid refrigerant to the crankcase of the compressor which caused damage to the working parts of the compressor or impaired the lubricating qualities of the lubricant.

The chief object of the present invention is to provide a method of returning oil to the compressor of a refrigeration system while preventing return of liquid refrigerant.

An object of the invention is to provide a method of returning oil from an accumulator of a refrigeration system in which the accumulator serves as a reservoir for liquid refrigerant, but which will not accumulate oil.

A further object is to provide a method of returning oil from an accumulator of a refrigeration system in which the accumulator is connected to the suction line of the system whereby passage of gaseous fluid in the suction line induces oil collected in the accumulator to return to the compressor, the connection being so designed that free flow of liquid refrigerant therein is restricted by vaporization thereof, the bubbles serving to block the outlet of the accumulator preventing or retarding free flow of refrigerant thereto. Other objects of the invention will be readily perceived from the following description.

This invention relates to a method of returning oil from an accumulator of a refrigeration system to the comice pressor of the refrigeration system. In the system, an evaporator is connected by the suction line to the com pressor; An accumulator is disposed inthe suction line and servesas a reservoir forli'quid refrigerant. collects tosome extent im the accumulator. The bottom of the accumulator-"isconnected to thesuction line by a conduit of small diameter. The outlet in the accumulator is. also ofsmall diameter; At least a-porti'on of the conduit extends downward below theaccumulator; the downwardextension is exposedto ambient atmosphere whereby its temperature is higher than the temperature in the accumulator. Passage of gaseous refrigerant in the suction line induces oil collected in the accumulator through the conduit and returns the oil to the compressor. However; if no oil is: present in the accumulator, liquidrefrigerant may attempt to return to the compressor which would beundesirable: Since the downward portion of the conduit is at a higher temperature than the accumulator; some portion of" the refrigerant entering the conduit is vaporized, the bubbles of gaseous refrigerant rising in the conduit to restrict free flow of liquid refrigerant therein and serve to block free flow of liquid refrigerant into the conduit.

The attached drawing illustrates a preferred embodiment of: my invention, in which- Figure lis a. diagrammatic View of a refrigeration system illustrating the manner-in which the method of the present invention may bepracticed; and

Figure 2 is arrexaggerat'ed sectional View disclosing the construction of the accumulator and connecting conduit;

Referring to the drawing, there is shown a refrigeration: system including a compressor 2 connected to condenser 3 by discharge line 4. Condenser 3 is connected to an evaporator 5 by liquid line 6. A suitable expansion device 7 such as a capillary tube or a thermal expansion valve is disposed in line 6 to regulate the refrigerant flowing to the evaporator 5. A suction line 8 connects the evaporator 5 and compressor 2. An accumulator 9 is disposed in the suction line 8 and acts as a reservoir for liquid refrigerant preventing such refrigerant flooding into the compressor and also serves to collect oil passing through the refrigeration system. The accumulator 9 is inclined downward to some extent to assure that liquid therein collects in a pool at one end 10; the suction line connections are made to the raised end of the accumulator.

At end 10 of accumulator 9, an outlet 11 of small diameter, is provided connected to a conduit 12. Conduit 12 includes a downward extending portion 13 and a second portion 14 which connects, as shown in Figure 2, with suction line 8. The passage of gaseous refrigerant through the suction line serves to induce oil collected in the accumulator to enter the suction line and to return such oil together with gaseous refrigerant to the compressor.

When all oil collected in the accumulator 9 has been withdrawn it will be appreciated any liquid refrigerant collected therein will attempt to pass through the conduit 12, induced by the passage of gaseous refrigerant in suction line 8. Conduit 12 is exposed to ambient atmosphere so that the temperature thereof is higher than the temperature in accumulator 9. The outlet 11 being of small diameter it will be appreciated any liquid refrigerant passing therethrough flashes to some extent. The heat transferred to the conduit portion 13 from the ambient atmosphere and outlet 11 cooperate to vaporize or produce a small series of bubbles 15 which serve to restrict free flow of liquid refrigerant in the conduit. Such bubbles 15 rise upward in the conduit portion 13 and aid in blocking outlet 11 to prevent to some extent passage Oil also 3 of liquid refrigerant therethrough. Any refrigerant able to seep through the barriers so provided is in gaseous form when it is drawn into the suction line 8 since portion 14 of conduit 12 is also exposed to the ambient atmosphere.

If it be desired to increase the formation of bubbles 15 at the accumulator outlet 11, fins 16 or similar heat concentrating means maybe disposed about conduit portion 13. Any suitable means of increasing the temperature of such conduit portion may be utilized.

This invention assures that oil carried through the refrigeration system is returned to the compressor. The method provided prevents liquid refrigerant being drawn into the compressor from the accumulator of the refrigeration system, which may result in serious damage to the compressor, It is particularly adapted for use with small refrigeration systems such as those employed in small self-contained air conditioning units, domestic refrigerators, freezers, and the like.

Whilel have described a preferred embodiment of the invention, it will be understood the invention is not limited thereto since it may be otherwise embodied in the scope of the following claims.

I claim:

1. In a method of returning oil from a downwardly inclined, substantially cylindrical accumulator of a refrigeration system to the compressor of said refrigeration system, the steps which consist in collecting oil and liquid refrigerant in the accumulator substantially separating oil and refrigerant in the accumulator, so as to collect a layer of oil in the lower portion of the accumulator, inducing oil from the lower portion of the accumulator into the suction line through a downwardly extending conduit connected to the lower portion of the accumulator and to the suction line and exposed to ambient atmosphere by the passage of gaseous refrigerant through the suction line, then, when oil has been substantially exhausted from the accumulator, permitting liquid refrigerant in the accumulator to enter the downwardly extending conduit, vaporizing liquid refrigerant in the downwardly extending conduit to produce a series of bubbles, and utilizing the bubbles so produced to restrict the accumulator outlet to the downwardly extending conduit thereby blocking free flow of liquid refrigerant through the outlet.

2. In a method of returning oil from a first zone of a refrigeration system to a second zone of the refrigeration system, the steps which consist in collecting oil and liquid refrigerant in the first zone, substantially separating oil and refrigerant into layers in the first zone, inducing the layer of oil from the first Zone through a conduit exposed to ambient atmospheres and returning the oil to the secend zone by the passage of gaseous refrigerant from a third zone to a second zone, then when oil has been substantially exhausted from the first zone, permitting liquid refrigerant in the first zone to enter the conduit, vaporizing liquid refrigerant in the conduitto produce a series of bubbles, and utilizing the bubbles so produced to restrict the outlet of the first zone thereby restricting free flow of liquid refrigerant through the outlet.

References Cited in the file of this patent UNITED STATES PATENTS 302,294 Suckert July 22, 1884 1,899,378 Zouck et al. Feb. 28, 1933 2,134,768 Threkeld Nov. 1, 1938 2,440,146 Kramer Apr. 20, 1948 2,512,758 Winkler June 27, 1950 2,614,402 Swart Oct. 21, 1952 FOREIGN PATENTS 89,935 Germany Mar. 18, 1896 

